Mercedes is still innovating. The floor (front and rear) development is significantly more complex (and not seen before) relative to the other contenders who have adaptations based on previous years' development. The diffuser shaping for vortices to interact with the strake vortices is very interesting too.
I do see Mercedes adopting a McLaren diffuser strake in the future.
What's very interesting is they clearly must have looked at a full 4 element upper diffuser strake, but decided to only do it at the edge for lateral diffuser expansion support. Wonder why they didn't do it for the rest of the width? One thought is that the vertical central rectangular section under the gearbox is being used to create more suction behind to encourage the other slots (and diffuser). As for the rest of the section between the gearbox to the edge, they may not be trying to work the airflow as hard, potentially as a result of the suspension positioning.